The present invention relates to a thermal processing apparatus for thermally processing an object to be processed in a vertical process tube.
In the fabrication of, e.g., semiconductor wafers, LCD substrate, etc. there are various thermal processing apparatuses for processing, such as oxidation, diffusion, annealing, CVD, etc. Technical problems with such thermal processing apparatuses require work towards the e.g., achievement of higher precision of processes, improvement of uniform temperature distribution in the same plane of an object to be processed, improvement of thermal processing efficiency, etc.
Recently semiconductor processes have been further micronized while the diameters of wafers, an object to be processed, have been increased from 8 inches to 12 inches. In addition, thermal processing apparatuses for homogeneously and efficiently processing large substrates, such as LCD substrates, etc. are needed. In accordance with increasing micronization of the processes and increased diameters of the object to be processed, higher precision of the processing, more uniform temperature distribution in the same plane of the object to be processed, and improved thermal processing efficiency are required. In addition, improved throughputs of the fabrication of the object-to-be-processed, whose diameters tend to be increased, are required.
Accompanying the increase of diameters of the object to be processed, the following problems are involved in the actual thermal processing.
That is, it is necessary to efficiently prevent slip and distortion of the object to be processed and improve uniformity of temperature distributions in the same plane of the object to be processed. To these ends, serious technical problems exist such as how to homogeneously heat the object to be processed, how to minimize temperature differences of the object to be processed between the central parts and the peripheral parts, which are caused by larger heat dissipation amounts of the peripheral parts than those of the central parts, and so on. It is necessary that, in accordance with the micronization of the processes the heat processing on the object to be processed be of higher precision, and contamination of the object to be processed be decreased. Accordingly technical problems that exist include how to conduct the thermal processing efficiently for short periods of time for homogeneous film quality and thicknesses in the same plane of the objects to be processed, how to decrease damage to the object to be processed by contamination due to heavy metals, etc., and so on.